Abstract

Abstract: A data set of long-term radon measurements in approximately 2800 houses in Bulgaria has been collected in National radon survey (2015-2016) under National Radon Program. The distribution of all radon data sets has been found to be log-normal. The main results of measured annual radon concentration in each for the 28 bulgarian districts are summarized. The arithmetic mean is 111 Bq/m3 and is approximately equal to the weighted average population on 108 Bq/m3.The object of the study is to assess the impact of building characteristics on variations in radon concentration. The article discusses the following building features: year of construction, type of base and facade of the measured dwellings and type of window frames in the buildings surveyed. Because more radon data are included in the current assessment, and the data set covers broader building factors, the current assessment better represents the radon exposure in Bulgaria. In conclusion, the complete results of National Survey provided a reliable estimate of the radon national distribution in bulgarian dwellings, and represent the basis for more detailed estimates of the impact of different factors on the indoor radon concentration.